Wood chippers are available for use with tractors having power takeoff shafts at their rears and which are capable of lifting the chippers and transporting them to a site where, when lowered onto the ground, they may be connected to the power takeoff shafts of the tractors.
Such chippers are of two types. In one type, the chipping units are coupled directly to the power takeoff shafts. This type of chipper has the disadvantageous feature that the rate of rotation of the chipping unit is limited to the R.P.M. of the shaft.
The other type of wood chipper employs a belt drive to enable the RPM of the chipping unit to be substantially increased thus enabling it to store more energy. In such chippers, the belted drive unit is interposed between the tractor and the chipping unit.
The weight of a wood chipper is an important factor as, in general, the capabilities of a wood chipper increase with its weight. Assuming the ability of a farm tractor such as a Ford 8N or a John Deere 1050 to lift a wood chipper, the weight transferred from the front to the rear wheels may cause the tractor to be difficult to control and increase the risk of tipping over on rough ground or on a steep grade. Larger, more powerful tractors are similarly prevented from carrying chippers large enough to allow efficient commercial whole tree chipping to be done.